Retaining device for rotary hooks



MRM

prl H5@ R. c. ROBERT RETAINING DEVICE FOR ROTARY Hooxs Filed Feb. 28, 1 946 ATTORNEYS Patented Apr. 25, 1950 NTED STATES TENT @ENCE Ramon Casas Robert, Geneva. Switzerland, as-

signer to Meiina S. A. Binningen, a corporation of Switzerland Application February 28, 1946, Serial No. 650,769 In Switzerland April 18, 1945 7 Claims.

The present invention relates to an improvement in sewing machines having a rotary hook. Such a device generally consists of two essential parts, viz. an inner part called the bobbin holder and adapted to support the bobbin, and an outer part rotating around the bobbin and carrying a hook for catching the loop formed by the upper thread and for passing the latter around the bobbin. The outer part also serves as a support and guide for the bobbin holder and would take the latter with it in its own rotary movement, if it was not for a retaining device which prevents this action and which maintains the bobbin holder stationary.

Numerous designs have been proposed for this retaining device. The simplest means consist in providing the bcbbin holder with an extension, bearing against a fixed stop located in the path of the aforementioned extension. As this stop prevents rotation in one direction only, the bobbin holder is free to rotate in the opposite direction for a fraction of a revolution at least. Such a device affords the possibility of removing the goods being sewn from the machine at standstill, without the upper thread remaining hooked in the rotary hook, but it has the inconvenience that, for every stitch, the upper thread having to make its way between said extension and stop, it must overcome an appreciable resistance, varying among other things with the rotational speed of the rotary hook. The upper thread is thus periodically subjected to sudden tensions, caus ing irregular seams, and noisy operation.

For the purpose of avoidingr these inconveniences, numerous retaining devices of various types have been suggested. Most of them have a stop intended to co-cperate with bearing surfaces provided on the bobbin holder, said stop being periodically caused to leave the cooperating bearing surface in order to leave a free for the upper thread during its travel round the bobbin. Some of these retaining devices comprise two stops, one of them remaining in a fixed position, the other one being carried by a rock ing arm, which periodically imparts a backward movement to the bobbln holder for the purpose of liberating the passage in front of the first stop. rIhissolution has the disadvantage of subjecting the bob'oin holder to oscillations which cause ob jectionable vibrations.

In other devices, swinging or rotating members are used having extensions reaching into recesses provided in the bobbin holder for the purpose of keeping same stationary, said extensions leaving periodically the corresponding recess to allow a free passage way for the upper thread. All these constructions have the great inconvenience of not allowing the withdrawal of the work from the machine at standstill, because the loop formed by the upper thread remains caught by the retaining device.

Moreover, in all the constructions mentioned,l the stops are provided on the periphery of the rotary hook at points which are either diametrically opposite to each other with respect to the axis of the rotary hook, or located on the same side of a plane passing through the rotary hook and needle axis. This arrangement has the inconvenience of making only a small fraction of the duration of a revolution of the rotary hook available for the period of oscillation or rotation of said retaining device. This means, that the latter must move at a rather high speed and that the resulting stopping forces exerted on the bobbin holder vary in magnitude and direction thus causing very disturbing vibrations.

It has also been proposed to mount the stops on a rotary member, tted with a slot for the thread. In this arrangement the stops are located in the immediate vicinity of the needle and on the same side of the plane passing through rotary hook and needle axes, thereby producing unfavourably located entrance and exit points of the upper thread.

Moreover, a common drawback oi all these constructions is that they provide no means for preventing the bobbin-holder, pulled towards the needle by the lower thread, from bearing against the rotary part of the rotary hook in the most unfavourable portion of its periphery, i. e. against the portion where it is cut away for the passage of the upper thread.

The retaining device, forming the object of this invention7 is free from the aforementioned inconveniences. t is distinguished from other retaining devices known, by two bobbin-holder prongs located in close vicinity and on two opposite sides of the needle, and on two different paths around the axis of said rotary hook and by two stops provided each with a single bearing face acting individually on the respective prong so as to continually prevent a rotational displacement of said bobbin-holder in the direction followed by the revolving part of said rotary hooi; and so as to allow at standstill of said machine said bobbinholder to perform a substantial rotational displacement in the opposite direction under the action ofva slight pull exerted on said upper thread, thus allowing the work to be removed from said 55 machine at standstill.

Simply stated, further objects of the inven tion are:

hook in such a way thattheforce exerted on them contains an upwardly directed vertical component releasing partially the vertical force exerted by the weight of said'boobin and bobbin-holdergin said rotary hook; :Further minor improvements whichwill become apparentfto one skilled in the art inl-the `Acourse of the following description.

,The drawings showv by wayy of Aexample aform of Vembodiment of the invention.

Figs. l, 2 and 3 are perspective views of the devce' seen in three'differentworking positions.

Fig. 4 is a'plan viewoffa portion of thel device.

Fig. 5 is a-perspective view of the device shown 0with its connections to "a work `feeding L HnisrnY of -a sewingv` machine.

'The device represented in--the drawings is invtended for usewith 'a-vertical axis rotary hook, l'making two revolutions "for every-stitch. The

rotary Vhook comprisesfa-,rotary anda stationary part. The rotaryzpart comprises-a cup l l, whose :cylindrical part is cut awayat l2 so as'to forni a hook i3, substantiallytangential to the needle iii of aV sewing machine not shown. Said cup l l Vis mounted rigidly on a shaft l5 driven in rotation by a shaft I6 in the'direction of 'the arrow by `means of two bevel gearsl'l and I8.

`The rotational speed of shaft l5 is'double that ,of 'driving shaft l5. Said cup' ll servesas sup port and housing for the stati onary part of the rotary hook, i. e. abobbin-holder i9 ,containing bobbin2ii carrying'the lower'thread 2l of the sewing machine. "The purpose of hook l2 is'to catch aloop formed by the upperthrea'd22 and .to pass it around..said..bobbin. ,.Bobbinvholder i@ held and guided bysaidcup 2|! ,wouldbecarried -alongby frictionbythemere rotation of, said cup .ifitwasnot preventedfrom sodoing. by a-.retainingdevice, forming Vthe object .ofthis invention and vwhich .maintains said bobbin-holder stationary.

The bobbinfholderis provided with a. horizontal extension23 cut -awayisotasto form two-.prongs 24 and 25 buttingagainst-.two bearing faces 2.5i

.andZ'l providedon an oscillating. member, whose shaft 28, parallel with'said driving `shaft ii, vis made to oscillate inxed bearings (not shown). Shaft I6 imparts an oscillating movement to shaft 28 by means of a cylindrical. cam 29 mountedV centrically on said shaft and alever. ufastened to said oscillating shaft.y Oneend of said lever is `bent so-as to form'acollar;aroundfshaft 2e. clamped bya screw4 3 l, permitting an angularad'- justmentof said-leveron said shaft 28. The other `end of-said lever ismaintaned in continuous contact with cam 29 by a springl 32wound on shaft 2,8, one end ofsaidspringresting onaiixed point, :the other end being held 'gon lever 3l;by faprong 33. Shaft 28 has, riveted to;it,-anarm 35i vlrithgan offset vane 35 and a groove, guiding a regulatable lil small plate 36. A clamping screw 37 allows the aforementioned plate to be adjusted relative to the shaft 28. The surfaces 26 and 21 acting as stops for the prongs 24 and 25 are provided respectively on the edges of vane 35 and sliding plate 36.

For reasons, .which shall :become apparent later, it must be-noted thatthe surfaces of contact between stops and prongs are chosen on two different radii with respect to the rotary hook .axis so as-.tovbe located on diierent paths around said axis. Said surfaces or butting faces 25 and 2l are portions Aof f conical surfaces having their axmcoincidingf with that of shaft 253 as shown in Fig. 4. The 'result of this arrangement is that thepoint of contact. of each of said but-ting faces lwithlits .corresponding bobbin-holder prong 24 and,25has its instantaneous motion directed in the plane tangent to said butting face at said point of contact. Thus, the oscillation of said stops 35 and -'causes no motion Aof thelbobbinholder around the `rotary vhook axis.

It should be noted that saidfcontactfpoints between said stops and said prongs are located vat twopoints practically vopposite toA one another with'respect to the needle axis TM "(seeFigfci, one in back and one in frontloflsaidvaxis). Stops 25 and 2l thusprevent bobbimholder i9 from 'being frictionally carried aroundbycupllfl.

The oscillatory Amotion of 'Yaxlef28, synchronised with the motions of hook l 3 and needleY l 4has`for its object toalternately cause oneorthe other stop to `retreat from the respective prong :24 or 125,

thereby preparing a free passage lway cfor that strand of the'loop formed by the'upper `thread whichls carried around by the hook.

Describing the various'functionsfrom theppoint ofview of the-operator of'said sewing machine with the rotary hook on theleft Vof -the needle axis:

Fig. l shows the {device-at the `momentfarm Vtl'reaches the upperdeadv pointof itsY movement.

Rear stop 2'! is in contact with'rear prong 25 and maintains bobbineholder lsstaticnary. "Loop22 justv formed bythe needle in its upwardmovement betweenprongs 221 and 25 has'been caught'by vrear prong 25 still bears against.buttingfaceZl.

At this point, itis necessary to notelthat, Lthe aforesaid clamping screw 31 allows the .device '..to

be adjusted during assembly. so` as to enable' both prongs to give simultaneouscontact with their respective stop.

Fig. 3 shows thedevice shortly 4before .arm .34

. has v reached 4its lowerY dead point. .Prong ,24 .re-

mains vin-contact with butting Vface 26, Vwhile a .passage way has been. freed betweenjfront `edgeof rear prong 2d and butting'face .1210i .-rearstop 35. Strand 22 of the loop being/.pulled .bythethread tensioning device .(not shown) .of the :sewing machine, the loopembracinglrearprong 25de -.creases in .size andfslidingalongthe :edgesnf prong 211i 'escapesffror'n the .rotarylhook .before .it may be vcaught againby'hook 13.

Subsequently, arm 34 has its motion reversed,

it moves upwards and reaches again the position shown in Fig. 1; during this time, the hook idles and performs a complete revolution.

From the above it may be seen that the described device has the following advantages:

(1) The arrangement of stops and prongspl'events the rotation of the bobbin-holder in one direction only, the direction in which said bobbin-holder would be carried by, the rotary part of the rotary hook. Owing to this feature and to the shapes given to'said stops and prongs, when the machine j stands still in a position not very far from that corresponding to the entrance or to the exit of the upper thread, the work may be removed freely from the sewing machine. The upper thread under a very slight pull may be freed from the rotary hook by causing the bobbin-holder to rotate backwards a portion of a revolution.

Both stops are placed in the immediate vicinity and on two opposite sides of the needle axis, the entrance of the loop being located in front `of the needle axis and the exit of the loop being located in back of the needle axis. This arrangement affords the largest possible time-interval between the instants of opening of the passage ways for the entrance and for the exit of the upper thread, thus allowing for a comparatively large amplitude for a, reasonably small velocity of the oscillating stops to be chosen. By reason of the vicinity of the two stops and of their position with respect to the rotary hook axis, the forces exerted by them on the prongs 0f the bobbin-holder have substantially the same magnitude and direction for all positions of said stops. There is thus no alternating force capable of causing vibrations of the bobbin-holder.

The resting edge of the two prongs as seen from the top (Fig. 4) leans backwards (angle d) in such a way that the forces exerted by the stops on the bobbin-holder counteract to a certain extent the tension exerted by the lower thread on the bobbin 'towards the needle. This feature prevents the bobbinholder from bearing on the cylindrical portion of the cup in the vicinity of the needle axis, thus avoiding an unfavourable guiding of the bobbin-holder in the cup, which would exist at the moment where both cut-outs in bobbin-holder and cup come in coincidence during the rotation of the cup, this relative position being shown in Fig. 3. rOwing to this particular arrangement the .guiding of the bobbin-holder on its 4periphery takes place at a point substantially remote from the cut-out of the bobbin holder I9 say practically in the directionof arrow 38.

The forces exerted by the stops on the vbobbin-holder have a verticali component acting upwardly, with the effect Aof reducing' the frictional forces on the horizontal bearing surfaces of the bobbin-holder in the cup. This upwards cornponentfresults"` from the fact, that the butting faces-of the stops are not vertical at their point f'contac't with the bobbin-holder prongs. In fact; the axis of revolution of the conical 4surfac'esZ and 2l of stops which coincide withethatof the axle Y' 28 is located at a level mubhlowefithan that: of theprongs 24 and 25 ofthe bobbin holderA Fig. 5 shows by way of example, how the described device can be combined with an automatic work-feeding mechanism of compact design. The oscillating member of the bobbin-holder retaining device and the automatic feeding mechanisrn are operated in common by eccentric 29 fastened to driving shaft I6. The feeding of the Work is produced by a toothed plate 4|, fastened to a moving arm 48, whose lower part is pivoted on a shaft 43 carried by a fork shaped member 44 oscillating with its shaft 45 in stationary bearings not shown. Both prongs 46 of said fork embrace cam 29. On its upper part, arm

42 is driven by a connecting rod 4l connecting a shaft 48 fastened to said arm with a shaft 49 driven by a connecting rod 52 driven itself by aforesaid eccentric 29. Fork shaped member 44 imparts a substantially vertical motion to toothed plate 4| while connecting rod 52 cooperating with a crank 5i), pivoted in 5| equipped with shaft 49 imparts a substantially horizontal motion to said toothed plate 4l. The

amplitude of latter said motion may be altered It is apparent that without departing from thev spirit and scope of the invention, it is possible to replace the angular oscillatory movement of aforesaid stops 35 and 35 by a rectilinear `oscillatory movement or more generally by a to-and-fro movement.

I claim:

l. In a sewing machine having a reciprocating needle for carrying an upper thread and a bobbin for containing a lower thread, a rotary hook having an axis of rotation parallel to the path of reciprocation of the needle, said rotary hook including a rotary member having a hook and a recess, a bobbin carrier mounted in said recess,.

a shaft for rotating said rotary member about its axis, a pair of spaced arms extending substantially radially outwardly from the bobbin carrier beyond the rotary hook, a pair of movable stops cooperating with said arms to prevent rotation of the bobbin carrier in the direction of rotation of the rotary hook, and means for oscillating said stops in a direction generally parallel to the shaft for driving the rotary member tov alternately position one stop in engagement with its cooperating arm and move the other stop away from contact with its cooperating arm to enable a thread loop to pass between the same.

2. In a sewing machine having a reciprocating cluding a rotary member having a hook and a recess, a bobbin carrier mounted in said recess, a shaft for rotating said rotary member about its axis, a pair of spaced arms extending substantially radially outwardly from the bobbin carrier' beyond the rotary hook, a pair of movable stops cooperating with saidarmg to prevent rotation of Athe bobbin carrier in the direction of rotation.4 of the rotary hook, and means for oscillating and d. said stops in "a direction generally parallel'to `the sh'aft for driving the rotary member to alternately position one stop in engagementv with its cooperating arm and move the other stop away from contact with its cooperating arm to enable a thread loop to pass between the same, said oscillating means beingdriven at a speed relative tothe rotary member driving shaft such thatl the rotary member ymakes two revolutions for each to and fro movement of the stops.

3. In a sewing machine having a reciprocating needle' for carrying an upper thread and a bobbin for containing'a lower thread, a rotary hook having an axis of rotation parallel to the path of reciprocation of the needle, said rotary hookincluding a rotary member having a hook anda' recess, a bobbin carrier mountedin said recess,

a: shaft for rotating said rotary member aboutv enable a thread loop to pass between the same,

saidl means comprising an oscillating shaft positioned perpendicularly to the shaft driving the rotary member and carrying said stops, a crank arm fixed to the oscillating shaft, a cam shaft, a cam on the cam shaft cooperating with the crank arm for driving the oscillating shaft, transmission rneans connecting the cam shaft to the shaft driving the rotary member so that the cam shaft rotates at 1/'2 the speed of rotation of the other shaft, and the stops make a single to and fro movement for each two revolutions of the rotary hook carrying member.

4. In a sewing machine having a reciprocating needle for carrying an upper thread and a bobbin for containing a lower thread, a rotary hook having an axis of rotation parallel to the path of reciprocation of the needle, said rotary hook including a rotary member having a hook and a recess, a bobbin carrier mounted in said recess, a shaft for rotating said rotary member about its axis, a pair of spaced arms extending substantially radially outwardly from the bobbin carrier beyond the rotary hook, a pair of movable stops cooperating with said arms to prevent rotation of the bobbin carrier in the direction of rotation of the rotary hook, and means for oscillate ir'ig said stopsl in a direction generally parallel to the shaft for driving the rotary member to alternately position one stop in engagement with its cooperating arm and move the other stop away from contact with its cooperating arm to enable a thread loop to pass between the same; said stops each having a single engaging surface co acting individually with the arms, said stops being located at different distances from the shaft ofv the rotarymember and said arms being of diifer-A ent'y lengths to cooperate and prevent angular clispl'acementl of said bobbin carrier in the direc# tion of rotation of the rotary member only, and

permitting upon stopping the machine an opposite angular displacement of the bobbin carrier` to enable removal of work from the machine.

forc'ontaining a lower thread,a rotary hook 'hav'- ingan axis of rotation parallel to the pathfoff' reciprocation of the'needle, said rotary hook including a rotary member having a hook and aV recess, a bobbin carrier mounted in said recess, a shaft for rotating said rotary member about its axis, a pair of spaced arms extending sub-v stantially radially outwardly from the bobbin carrier beyond the rotary hook, a pair of movable stops cooperating with said arms to prevent rotation of the bobbin carrier in the direction of rotation of the rotary hook, and means foroscillating said stops in a direction generally parallel to the shaft for driving the rotary member to alternately position one stop in engagement with its cooperating arm and move the other stop away from contact with its cooperating arm to enable a thread loop to pass-between the same, said stops each having a contact surface movable along the arc of a circle tangent to the cooperating surface ofthe arm to avoid vibration of the bobbin carrier.

6-` Ina sewing machine having a reciprocating the bobbin carrier in the direction of rota-tionV of the rotary hook, and means for oscillating said stops in a direction generally parallel to the shaft for driving the rotary member to alternately position one stop in engagement with its cooperating arm and move the other stop away from contact with its cooperating arm to enable a thread loop to pass between the same, the contact surfaces of the stops being approximately parallel to each other and to the corresponding surfaces of the arms, and said surfaces being oriented in such a manner that the bobbin carrier is subjected during oper-ation of the machine to a force of approximately constant value and the latter direction being approximately opposite to the force exerted on the carrier by the bobbin thread when tension is applied to said thread.

7. In a sewing machine having a reciprocating needle for carrying -an upper thread and a bobbin for containing a lower thread, a rotary hook having an vaxis of rotation parallel to the path of reciprocation of the needle, said rotary hook including a rotary member having a hook and a recess, a bobbin carrier mounted in said recess, a shaft for rotating said rotary memberrabout its axis, a pair of spaced arms extending substantially radially outwardly from the bobbin carrier beyondthe rotary hook, a pair of movable stops cooperating with said arms to prevent rotation of the bobbin carrier in the direction of rotation of the rotary hook, and means for oscillating said stops in a direction generally parallel to the shaft for driving the rotary 'member4 to alternately Apositi'onV onestop in engagement with its cooperating arm and move the other stop away from contact with its cooperating Aarm to enable a thread loop to pass between the same, said means comprising anoscillating shaft positioned perpendicnlarly -to the. shaft driving the rotary member and carrying said stops, a, crank arm xed-to'the oscillating shaft, a cam shaft, a cam :on the ,cam shaft cooperating with the crank arm forY drivl 10 ing the oscillating shaft, transmission means con- REFERENCES CITED necting the cam shaft to the shaft driving the rotary member so that the cam shaft rotates at mrg ftgvgerens are of record m the l/2 the speed of rotation of the other shaft, and

the stops make a single to and fro movement for 5 UNITED STATES PATENTS each two revolutions of the rotary hook carrying Number Name Date member and a work feed mechanism having a 2,236,830 Myers Apr. 1, 1941 cam follower cooperating with said cam for operating the same.

RAMON CASAS ROBERT. lo 

